1. Field of the Invention
The present invention relates to damped flywheels, especially for motor vehicles, of the kind comprising two coaxial masses, one of which, referred to as the first mass, is adapted to be coupled in rotation to a driving shaft, such as the crankshaft of an internal combustion engine, the other one, referred to as the second mass, being adapted to be connected to a driven shaft, such as the input shaft of a gearbox, and of the type in which the two masses are mounted coaxially through an interposed bearing, such as a ball bearing, and in which coupling means are interposed between the two masses so as to couple the second mass to the first mass.
The coupling means may comprise springs acting either circumferentially or radially, or in another version these means may be of a centrifugal type as described in the document FR-A-1 598 557.
In all cases, the second mass constitutes the reaction plate of a friction clutch, and for this purpose it offers a friction surface to the friction disc which is part of the said clutch. Thus the second mass is arranged to be mounted in rotation on a driven shaft through the interposed friction disc, that is to say in a disconnectable manner.
The friction liners of the friction disc tend to become heated in service, and the same is then true for the second mass which defines the reaction plate.
Under severe driving conditions, this second mass may reach very high temperatures, and this is why, in the document FR-A-1 598 557, ventilation holes were provided in the second mass, between the bearing and the friction surface of the second mass, in order to reduce the temperature in the region of the bearing. These holes thus prevent any risk of over-heating of the bearing. They are located close to the bearing.